Preliminary Study on the Characteristics of Pteridophyte Flora in the Loess Plateau

The classification, composition and characteristics of pteridophyte flora in the Loess Plateau were investigated.The results revealed that the pteridophytes in the Loess Plateau consisted of 184 species and 3 varieties,53 genera and 26 families.Of the pteridophytes,Athyriaceae (30 species),Dryopteridaceae (26 species),Polypodiaceae (20 species),Aspleniaceae (12 species),Selaginellaceae (12 species),Sinopteridaceae (11 species),Hermionitidaceae (10 species) covered higher proportions.These 7 families contained 121 species,which accounted for 64.71% of the total number of pteridophyte species in the plateau.The species with relatively higher proportions belonged to Dryopteris (13 species), Selaginella (12 species), Asplenium (11 species), Polystichum (11 species), Athyrium (10 species), Lepisorus (10 species), Adiantum (9 species) and Woodsia (9 species).These 8 genera occupied 85 species,which comprised 45.46% of the total number of pteridophyte species in the plateau.The pteridophyte genera occurring in the pteridophyte flora in the Loess Plateau fell into fifteen areal types.Tropical and subtropical areals covered 18 genera,which accounted for 41.86% of the total genus number;North temperate and cool temperate areals took 22 genera,which accounted for 51.16% of the total genus number (not including cosmopolitan genera),and most of which,totaling 16 genera,occupied Asian areals and accounted for 37.20% of the genus total,and this showed that the pteridophyte flora in the Loess Plateau belonged to a temperate type.The geographical elements of the pteridophyte flora mainly consisted of the pteridophytes occurring in northern China in addition to those occurring in central China,east China,northeast China,northwest China and southeast China.However,only one pteridophyte genus was endemic to China.